<template>
    <div class="pagination">
        <button :disabled="pageNo==1" @click="$emit('getPageNo',pageNo-1)">上一页</button>
        <button v-if="startNumAndEndNum.start > 1" @click="$emit('getPageNo',1)" :class="{active:pageNo==1}">1</button>
        <button v-if="startNumAndEndNum.start > 2">···</button>

        <button v-for="(page,index) in startNumAndEndNum.end" :key="index" v-if="page >= startNumAndEndNum.start" @click="$emit('getPageNo',page)" :class="{active:pageNo==page}">{{ page }}</button>

        <button v-if="startNumAndEndNum.end < totalPage-1">···</button>
        <button v-if="startNumAndEndNum.end < totalPage" @click="$emit('getPageNo',totalPage)" :class="{active:pageNo==totalPage}">{{ totalPage }}</button>
        <button :disabled="pageNo==totalPage" @click="$emit('getPageNo',pageNo+1)">下一页</button>

        <button style="margin-left: 30px">共{{totalPage}}页</button>
    </div>
</template>

<script>
export default {
    name: "Pagination",
    props:['pageNo', 'pageSize', 'total', 'continues'],
    computed:{
        //总共多少页
        totalPage(){
            //向上取整Math.ceil方法
            return Math.ceil(this.total/this.pageSize)
        },
        //计算出连续的页码的起始数字与结束数字【连续的页码数最少为5】
        startNumAndEndNum(){
            //通过解构赋值取出this身上的属性
            const {continues,pageNo,totalPage} = this
            //先定义两个变量存储起始数字和结束数字
            let start=0,end = 0
            //不正常情况当总页数没有连续页数多
            if(continues > totalPage){
                start = 1
                end = totalPage
            }else {
                //正常情况总页数大于连续页数
                start = pageNo - parseInt(continues / 2)
                end =  pageNo + parseInt(continues / 2)
                //把出现不正常的现象start等于0或负值纠正
                if(start < 1){
                    start = 1
                    end = continues
                }
                //把不正常的end大于页码数情况纠正
                if(end > totalPage){
                    end = totalPage
                    start = totalPage - continues + 1
                }
            }
            return {start , end}
        }
    }
}
</script>

<style lang="less" scoped>
.pagination {
    text-align: center;
    button {
        margin: 0 5px;
        background-color: #f4f4f5;
        color: #606266;
        outline: none;
        border-radius: 2px;
        padding: 0 4px;
        vertical-align: top;
        display: inline-block;
        font-size: 13px;
        min-width: 35.5px;
        height: 28px;
        line-height: 28px;
        cursor: pointer;
        box-sizing: border-box;
        text-align: center;
        border: 0;

        &[disabled] {
            color: #c0c4cc;
            cursor: not-allowed;
        }

        &.active {
            cursor: not-allowed;
            background-color: #409eff;
            color: #fff;
        }
    }
}
</style>